"I have two young sons and I will sue the mf that teaches either of them about homosexuality."
I await patiently for the case of St. Denis vs. Society at Large.
"They are too young to learn about sex [...]"
Then don't teach them about sex. Explain to them why two people of the same gender are together: for the same reason that two people of opposite genders would be.
Wow. That was hard. Hope the graphic descriptions of sex weren't too much for you.
"[...] and I should have some rights as a parent."
You have the right to shelter your kid from reality and fuck them up, just like every other parent. Fortunately most decide not to exercise such rights.
"What do you think about the school in San Francisco that wants to use a book about a gay penguin couple in kindergarten book and does not want to allow parents the right to opt out."
I think they chose an appropriate animal. As I keep pointing out, penguins are notorious for such behavior.
"5 year olds learning about homosexuality is obscene."
They're not learning about "homosexuality" you twit. At least not in the way you seem to be implying. They're having a specific part of modern society explained to them in a way they can understand.
"5 year olds learning about sex period is obscene."
First of all, there's nothing wrong with a five year old having the biology of sexual reproduction explained to them. The actual mechanics might be a bit much, sure, but the biology behind it is nothing to hide.
Second, nobody's teaching five year olds about "sex" ("sex" as in what your dirty little mind conjures up at the word).